JPH0426578B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] A terminal device polled from the main device is restarted when transmission from the terminal device to the main device is completed and when reception of each word from the main device is completed. one monitoring timer is provided,
The occurrence of an abnormality is detected when this timer measures a predetermined time.

[Industrial application field]

The present invention relates to a configuration for detecting an abnormality in a terminal device in a system including a large number of terminal devices polled by a main device.

[Conventional technology]

In a conventional terminal device of this kind, from the time the terminal device sends a transmission end character (for example, “EOR”) to the main device, an end character (for example, “ A response time monitoring timer that measures the time until receiving the end character (EOR), and a character interval monitoring timer that is restarted each time it detects each character received from the main device and measures the time until it detects the received end character. An abnormality is detected when one of these timers overflows.

[Problem that the invention seeks to solve]

In the conventional terminal device as described above, it was necessary to provide two timers as described above, and it was also necessary to control starting, stopping, and restarting each of these timers.

[Means for solving problems]

FIG. 1 is a diagram illustrating the principle of the present invention, showing character reception detection means 2 for detecting that a character has been received from the main device, and end character detection means for detecting that a transmission end character has been sent to the main device. 34, an OR circuit 4 for calculating the logical sum of the detection outputs of these detection means 2 and 3, and a restartable monitoring timer 5.

[Effect]

FIG. 2 is a time chart for explaining the principle of the present invention, in which figure a shows a received signal, figure b shows a transmitted signal, and figure d shows the counted value of the monitoring timer 5 of FIG.

When the terminal device receives the character C including the end character from the main device, the character reception detection means 2 sends a detection signal for each received character to the monitoring timer 5 via the OR circuit 4, and sets this timer to "0". Immediately after returning to , restart the clock to start counting, and repeat this every time a character is received. Further, when this terminal device sends out an end character signal E indicating the end of transmission, for example, an "EOR" signal, the end character detection means 3 sends the detection signal to the OR circuit 4 in the same manner as described above.
from there to the monitoring timer 5 to restart it.

As a result, the count value of timer 5 becomes as shown in figure c, and if timer 5 overflows, the polling signal or data signal is received from the main device and transmitted from this terminal device within a predetermined time. By using this overflow signal as an abnormality signal, an abnormality can be detected.

〔Example〕

FIG. 3 is a time chart showing the operation of the embodiment of the present invention, and shows an example of one terminal device when transmission between the main device and a large number of terminal devices is performed by the polling/selecting method. , the transmission time between the main device and the terminal device is ignored.

In the same figure, figure a is the count value of a monitoring timer similar to that in the conventional technology provided in the main device, figure b is the signal from the main device received by the terminal device, and figure c is
The figure shows the signal sent from the terminal device to the main device, the figure d shows the counted value of the monitoring timer of this terminal device, and the known transmission control characters are shown in figures b and c. There are, but
“EOR” is a character indicating the end of transmission, “ENQ” is a response request character, and the “EOR” and “ENQ” characters cause the main device to poll this terminal device, but other transmission control Since the functions of characters are well known and are not directly related to the present invention, a detailed explanation thereof will be omitted. It goes without saying that the selection signal for connecting this terminal device to the main device has already been removed in the receiving circuit or the like.

When the main device polls this terminal device using the “ENQ” signal and “EOR” signal as shown in Figure a, the monitoring timer 5 of the terminal device
(Fig. 1) is restarted by the output from the character reception detecting means 2 that has detected these signals via the OR circuit 4, and the "EOR" of the response signal sent from this terminal device in response to this polling. ``When the character detection means 3 detects the end of sending the signal, the count value is increased until the signal is restarted. “STX” indicates the start of transmission.
The count value is increased from 0 until the signal , arrives.

In the data part transmitted from the main unit following this "STX" signal, the monitoring timer 5 is restarted for each character, so the count value of this timer is an abbreviation that corresponds to the transmission time of 0 and 1 characters. When the terminal device receives an “EOR” signal indicating the end of transmission from this signal, it sends a reception completion signal “ACK” to the main device, but when the end of this signal The monitoring timer 5 is restarted again by the "EOR" signal indicating the polling signal, and increases its count value until it receives the "ENQ" signal of the next polling signal.

Therefore, the count value of the monitoring timer 5 will be a value depending on the communication status between the main device and the terminal device, and if the communication is not going smoothly, the count value will change to a predetermined count value, e.g. Since the monitoring timer reaches a value at which it overflows, an abnormality may be reported when the counted value of the monitoring timer exceeds this predetermined value.

In Fig. 3, the counted value of the monitoring timer of the main device is shown in Fig. a, and this monitoring is performed after the main device sends the end character to the terminal device and then receives the end character of the response from the terminal device. It monitors whether or not there is an abnormality in the terminal device by measuring the time until the main device and the terminal device do so. An abnormality can also be detected by transferring the values from the terminal device to the main device and comparing them.

[Effects of the Invention] According to the present invention, not only is it sufficient to provide one monitoring timer for the terminal device, but also only restarting is sufficient to control this monitoring timer, so it is possible to start, stop, and reset two monitoring timers. Compared to conventional techniques that perform control such as the above, it is possible to achieve a special effect of significantly simplifying both the configuration and control.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle of the present invention, FIG. 2 is a time chart explaining the principle of the present invention, and FIG. 3 is a time chart explaining the operation of an embodiment of the present invention. 1 is a terminal device, 2 is a character reception detection means, 3 is an end character detection means, 4 is an OR circuit, and 5 is a monitoring timer.

Claims (1)

[Scope of Claims] 1. In a terminal device in a system that is polled by the main device and transmits a termination character to the main device at the end of transmission, the terminal device 1 is capable of indicating that it has received each character from the main device. Character reception detection means 2 for detecting, end character detection means 3 for detecting that the end character has been sent from this terminal device to the main device, and an OR circuit for obtaining the logical sum of detection outputs from these detection means 2 and 3. 4 and a monitoring timer 5 that is restarted by the output of the OR circuit, and the timer detects the occurrence of an abnormality by measuring a predetermined time. A terminal device with an anomaly detection function.